With improved spectroscopic measurements enhanced correlation due to spatial confinement near surfaces and interfaces
of nano-structures became apparent which made it imperative to take the frameworks of computation of electronic structure beyond
the mean field regime leading to formidable increase in computational complexity and cost.
While much effort in this direction has been underway in terms of improving the exchange-correlation functionals
[1]} to include effects of many-electron interactions within the KS energy eigen-spectrum,
the GW approximation [2]} of the many body perturbation theory (MBPT) [3]}, [4]} is so far the most general abinitio framework to unmissably account for correlations starting from the KS single particle states.
However, both the approaches are computationally expensive and almost prohibitive for systems
with thousands of atoms. These limitations have led to attempts to incorporate effects of correlations within the tight-binding(TB) frameworks.
Efforts reported in recent years mostly improve TB parameters [5]}, [6]}, [7]}, [8]}, [9]} by matching QP structure
in specific systems and orbital subspaces.
